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Passive switching mixer volatge conversion gain calculation and its varition with frequency

Last post Wed, Jan 15 2014 7:15 PM by lahsivece. 14 replies.
 Started by lahsivece 09 Jan 2014 09:21 PM. Topic has 14 replies and 5541 views
• Thu, Jan 9 2014 9:21 PM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Passive switching mixer volatge conversion gain calculation and its varition with frequency
 Hi All,I am trying to do a passive switching mixer volatge conversion gain simulation. The circuit consists of a MOS transistor driving a resistive load. The gate of MOS is driven by a rail to rail square pulse. I tried the steps given in the Application note "Mixer design using Spectre RF " , but it didn't give meaningful results.Is there any application note that deals specifically with passive switching mixers with LO being driven by a rai to rail signal or a similar situation ?Best RegardsVishal
• Post Points: 20
• Fri, Jan 10 2014 7:17 AM

Re: Passive switching mixer volatge conversion gain calculation and its varition with frequency
 Vishal,There are some challenges with measuring IP3 with passive mixers due to limitations of certain device models (e.g. bsim3v3 and bsim4) - there are a number of academic papers on this problem. But I'm not sure whether this is what you mean by "didn't give meaningful results". That's a rather open statement...Kind Regards,Andrew.
• Post Points: 35
• Sun, Jan 12 2014 8:10 AM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer volatge conversion gain calculation and its varition with frequency
 Hi Andrew,Sorry for not specifying the problem correctly. I am not getting correct gain (loss) out of the passive mixer . My test bench looks like following:c1=500fFConversion gain was calculated using pss+swept pac. For pss analysis , # of harmonics set to 0 . Port0 is dc type (based Spectre RF simulation manual)  . In Swept pac # of sidebands  was set to 2. The input.scs looks like following:// Library name: MIXER_CHARACTERIZATION// Cell name: RX_MIXER_FUNDAMENTAL_RZ_MOS_PSF_PXF// View name: schematicPORT0 (RF 0) port r=50 dc=600m type=dc freq=frf dbm=vrf pacmag=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloM0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1R0 (IF 0) capacitor c=c1simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfpss  pss  fund=500M  harms=100  errpreset=moderate  annotate=statuspac  pac  start=1K  stop=500M  maxsideband=2  annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpubThe conversion gain for h=-1 is shown below. I am getting a positive gain whcih doesn't make any sense to me . Please advise what is wrong with this way of simulating mixer conversion gain.The gain at 10MHz If calculated by using pss analysis followed by a dB20 peak measurement comes as  -4.7dB. Test bench looks like (c1=500f) // Library name: MIXER_CHARACTERIZATION// Cell name: RX_MIXER_FUNDAMENTAL_RZ_MOS_SW// View name: schematicR0 (IF 0) capacitor c=c1M0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloV0 (RF 0) vsource dc=600.0m type=sine ampl=vrf freq=frfsimulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfdcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=statusdcOpInfo info what=oppoint where=rawfilepss  pss  fund=10M  harms=200  errpreset=conservative+    annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpub                                     ThanksWith Best RegardsVishal
• Post Points: 5
• Sun, Jan 12 2014 8:23 AM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer volatge conversion gain calculation and its varition with frequency
 Hi Andrew , Sorry for not being clear. I am not getting a correct voltage gain from passive swictging mixer . The test bench looks like following :The input.scs file is :// View name: schematicPORT0 (RF 0) port r=50 dc=600m type=dc freq=frf dbm=vrf pacmag=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloM0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1R0 (IF 0) capacitor c=c1simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfpss  pss  fund=500M  harms=100  errpreset=moderate  annotate=statuspac  pac  start=1K  stop=500M  maxsideband=2  annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpub c1=500f The simulated gain curve from pss+swept pac is I belive that this is wrong. I also calculated gain as VIF/VRF from PSS analysis  which at 10MHz IF comes to be -4.6dB. The input.scs looks like folowing :// Cell name: RX_MIXER_FUNDAMENTAL_RZ_MOS_SW// View name: schematicR0 (IF 0) capacitor c=c1M0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloV0 (RF 0) vsource dc=600.0m type=sine ampl=vrf freq=frfsimulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfdcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=statusdcOpInfo info what=oppoint where=rawfilepss  pss  fund=10M  harms=200  errpreset=conservative+    annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpubPlease advise as to what is going wrong with a pss+swept pac simulation. Thanks,With Best RegardsVishal
• Post Points: 20
• Tue, Jan 14 2014 2:38 AM

Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Vishal,There are no pictures in your posts. You can attach pictures via the Options tab when posting a reply.Regards,Andrew.
• Post Points: 20
• Tue, Jan 14 2014 5:18 AM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Andrew,Pictures were attached . Any way here is the whole post again Hi Andrew , Sorry for not being clear. I am not getting a correct voltage gain from passive swictging mixer . The test bench looks like following : Please refer to imageThe input.scs file is :// View name: schematicPORT0 (RF 0) port r=50 dc=600m type=dc freq=frf dbm=vrf pacmag=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloM0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1R0 (IF 0) capacitor c=c1simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfpss  pss  fund=500M  harms=100  errpreset=moderate  annotate=statuspac  pac  start=1K  stop=500M  maxsideband=2  annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpub c1=500f The simulated gain curve from pss+swept pac is Please refer to gain_curve.png image.I belive that this is wrong. I also calculated gain as VIF/VRF from PSS analysis  which at 10MHz IF comes to be -4.6dB. The input.scs looks like folowing :// Cell name: RX_MIXER_FUNDAMENTAL_RZ_MOS_SW// View name: schematicR0 (IF 0) capacitor c=c1M0 (IF LO RF 0) N_12_RF wf=5u lf=120.0n nf=4 m=1V1 (LO 0) vsource type=pulse val0=0 val1=1 period=tlo width=d*tloV0 (RF 0) vsource dc=600.0m type=sine ampl=vrf freq=frfsimulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \    checklimitdest=psfdcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=statusdcOpInfo info what=oppoint where=rawfilepss  pss  fund=10M  harms=200  errpreset=conservative+    annotate=statusmodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts  where=rawfilesaveOptions options save=allpubPlease advise as to what is going wrong with a pss+swept pac simulation. Thanks,With Best RegardsVishal gain_curve.png
• Post Points: 20
• Tue, Jan 14 2014 10:25 AM

Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 The pictures were not attached. If you paste the pictures in the post, it doesn't work - because they don't get uploaded to the forum server. So in your last post there was only one picture (the PAC output response) - but I think the text talks about a picture of the testbench too.Regards,Andrew.
• Post Points: 20
• Tue, Jan 14 2014 7:10 PM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi , Please find testbench image attached.  testbench.png
• Post Points: 20
• Wed, Jan 15 2014 3:14 AM

Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 I'd suggest you contact customer support. I'm a bit pushed for time this week to take a look - maybe somebody else on the forum can try it.Regards,Andrew.
• Post Points: 20
• Wed, Jan 15 2014 6:01 AM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Andrew,It's not an issue. I will  contact customer support for the same. RegardsVishal
• Post Points: 20
• Wed, Jan 15 2014 11:15 AM

• Tawna
• Joined on Fri, Jul 11 2008
• Snohomish, WA
• Posts 209
• Points 5,535
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency

Looks like my earlier post didn't make it onto the forum...

I agree with Andrew - this sort of question is best handled by Customer Support - they can dedicate more time and energy to answer questions.

There is an existing Solution on Cadence Online Support that you may want to look at:

Also, if you are using BSIM transistor models in your circuit, see this paper:

LINFET: A BSIM Class FET Model with Smooth Derivatives at Vds=0

by Lawrence F. Wagner, C. Michael Olsen.

IBM Systems & Technology Group, Global Engineering Solutions.

http://www.nsti.org/procs/Nanotech2007v3/7/W79.604

best regards,

Tawna

Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 20
• Wed, Jan 15 2014 7:01 PM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Tawna,Thanks for the information. I have already raised this issue with customer support. Best Regards,Vishal
• Post Points: 20
• Wed, Jan 15 2014 7:06 PM

• Tawna
• Joined on Fri, Jul 11 2008
• Snohomish, WA
• Posts 209
• Points 5,535
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Vishal,  What is the Case number and I'll keep an eye on it. best regards,tawna  Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 20
• Wed, Jan 15 2014 7:14 PM

• Tawna
• Joined on Fri, Jul 11 2008
• Snohomish, WA
• Posts 209
• Points 5,535
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Vishal,  I already found it.   No need to respond.best regards,Tawna Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
• Post Points: 5
• Wed, Jan 15 2014 7:15 PM

• lahsivece
• Joined on Tue, Oct 2 2012
• Posts 28
• Points 440
Re: Passive switching mixer voltage conversion gain calculation and its variation with frequency
 Hi Tawna ,Case Number assigned is  45539809.Best RegardsVishal
• Post Points: 5